Dental and medical practitioners routinely perform dental/medical procedures that typically involve using a tool such as a file, bur, cutter, reamer, or polisher powered by a motor system to cut a patient's tooth, bone, or soft tissue. For example, when a patient has a decaying and/or infected tooth, a dentist or other medical technician will often use a file or reamer to remove the dental pulp from the patient's tooth and preserve the health of the patient's tooth and/or jaw. And, when a patient has a chipped tooth or a cavity, a dentist or other medical technician will often use a bur to remove some of the tooth's enamel to prevent further, additional damage to the tooth. To remove the dental pulp from a tooth the dentist or other medical technician inserts a file or reamer into the tooth's root canal. To remove enamel from a tooth the dentist or other medical technician places a burr or other type of tool on the region of the tooth's enamel to be removed. The motor of the motor system then rotates the tool to cut and/or abrade tissue and/or enamel from the patient's tooth.
There are two general types of rotary motion that the tool performs during such procedures—single-direction rotation and reciprocating rotation. During single-direction rotation, the tool rotates primarily in one direction, clockwise or counterclockwise. To avoid unwanted damage to the patient and the tool, the torque experienced by the tool as it rotates is monitored. If the torque exceeds a desired limit, then the tool is rotated in the opposite direction for a brief moment to unbind it. Then the tool's rotation is again reversed so that it resumes rotation in the direction in which it cuts and/or abrades. During reciprocating rotation, the tool rotates in two, opposite directions, sequentially. The trigger for reversing rotational direction is often a predetermined angular displacement or the end of a predetermined period of time.
Using single-direction rotation often provides good cutting efficiency because the tool rotates for longer periods of time in the direction that the tool is designed to cut and/or abrade. Using the reciprocating rotation often provides a dentist or other medical technician a good feel for the procedure because the motor does not continuously power or load the tool in a substantially-single direction.
Thus there is a need for a system that provides the two general types of rotary motion and can provide either type of rotary motion in response to the conditions experienced during the a procedure.